Chapter 3-04: Diseases and Pathophysiology in Critical Care Medicine

SIRS, SEPSIS, SEVERE SEPSIS, AND SEPTIC SHOCK

• Introduction:

  • - Sepsis exists on a clinical spectrum of illness severity, with septic shock being the most severe

  • - Two major clinical approaches to a patient with suspected sepsis:

    • qSOFA is an assessment score used to detect early sepsis. It is easily performed at the bedside and is best suited for triage and early assessments, as it is well validated in patients outside of the ICU.

    • Older definition using the Sepsis-2 guidelines remains the most widely used and preferred approach for grading the severity of sepsis in the ICU.

      • - Note on Sepsis-3 guidelines (2016): SIRS and severe sepsis were dropped from these guidelines. Instead, Sepsis-3 defines sepsis as a rise in SOFA score of ≥2 points and septic shock as hypotension requiring vasopressors and an elevated lactate.

• Sepsis II definitions:

  • - Systemic inflammatory response syndrome (SIRS): Must meet at least two of four criteria

    • Temp <36°C or >38°C

    • HR >90 bpm

    • RR >20 breaths/min or PaCO₂ <32 mmHg

    • WBC >12K or <4K or >10% bands

  • - Sepsis: SIRS + suspected infection

  • - Severe sepsis: Sepsis + acute organ dysfunction

    • Acute organ dysfunction

      • - Hypotension (SBP <90 mmHg or MAP <70 mmHg)

      • - Hypoxemia (P/F <300)

      • - Oliguria (UOP <0.5 cc/kg/hr)

      • - Renal injury (Cr increase >0.5)

      • - Coagulopathy (INR >1.5)

      • - Thrombocytopenia (Plt <100K)

      • - Hyperbilirubinemia (Total bilirubin >4)

      • - Lactate >2

      • - New altered mental status

  • - Septic shock: Hypotension due to sepsis despite adequate fluid resuscitation (classically 30 cc/kg), as well as signs of hypoperfusion

• Sequential Organ Failure Assessment (SOFA):

  • - Alternative scoring system that can be used to predict the clinical outcome of critically ill patients and used in the Sepsis-3 guidelines. Takes into account Glasgow Coma Score (GCS), renal function, liver function, coagulopathy, and respiratory status (see Table 3.3)

  • - qSOFA (Quick SOFA) is a bedside assessment for early detection of suspected sepsis

    • Criteria: 1 point for each

      • - RR ≥22 breaths/min

      • - Altered mentation

      • - SBP ≤ 100 mmHg

    • Positive score is ≥2

    • Implications

      • - Positive score should prompt evaluation for end-organ dysfunction and calculation of full SOFA score

      • - Scores of 2–3 associated with higher in-hospital mortality

      • - Easily identified at the bedside and can be repeated as clinical changes occur

      • - Conflicting data on use in the ICU, may be more useful outside the ICU but research is ongoing

      • - See Table 3.4 for types of shock and associated features

• Pathophysiology:

  • - Infection causes proinflammatory cytokine storm (TNF-a, IL-1), “malignant intravascular inflammation”

  • - In infection, microorganism factors such as bacterial cell wall components (LPS) and bacterial products (toxins) may cause inflammatory reaction

  • - Inflammation leads to low systemic vascular resistance (SVR), fever, leukocytosis

  • - Cellular injury occurs, which can lead to further organ dysfunction:

    • Tissue ischemia from metabolic autoregulatory failure and hypoperfusion

    • Mitochondrial dysfunction and cell death

• Management:

  • - Antibiotics and infection control:

    • Start broad, empiric IV antibiotics within 1 ...